diff --git a/gcc/rust/typecheck/rust-tyty-subst.cc b/gcc/rust/typecheck/rust-tyty-subst.cc
index 976f6af12a5..26afe1bd491 100644
--- a/gcc/rust/typecheck/rust-tyty-subst.cc
+++ b/gcc/rust/typecheck/rust-tyty-subst.cc
@@ -934,27 +934,8 @@ SubstitutionRef::monomorphize ()
 	  auto associated
 	    = Resolver::lookup_associated_impl_block (bound, binding,
 						      &ambigious);
-	  if (associated == nullptr && ambigious)
-	    {
-	      // go for the first one? or error out?
-	      auto &mappings = Analysis::Mappings::get ();
-	      const auto &type_param = subst.get_generic_param ();
-	      const auto *trait_ref = bound.get ();
-
-	      rich_location r (line_table, type_param.get_locus ());
-	      r.add_range (bound.get_locus ());
-	      r.add_range (mappings.lookup_location (binding->get_ref ()));
-
-	      rust_error_at (r, "ambiguous type bound for trait %s and type %s",
-			     trait_ref->get_name ().c_str (),
-			     binding->get_name ().c_str ());
-	      return false;
-	    }
-
 	  if (associated != nullptr)
-	    {
-	      associated->setup_associated_types (binding, bound);
-	    }
+	    associated->setup_associated_types (binding, bound);
 	}
     }
 
diff --git a/gcc/testsuite/rust/compile/issue-3403.rs b/gcc/testsuite/rust/compile/issue-3403.rs
new file mode 100644
index 00000000000..ced6b4efd97
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-3403.rs
@@ -0,0 +1,38 @@
+pub struct Foo {
+    a: i32,
+    // { dg-warning "field is never read" "" { target *-*-* } .-1 }
+}
+pub struct Bar(i32);
+
+#[lang = "sized"]
+trait Sized {}
+
+pub mod core {
+    pub mod default {
+        pub trait Default: Sized {
+            fn default() -> Self;
+        }
+
+        impl Default for i32 {
+            fn default() -> Self {
+                0
+            }
+        }
+    }
+}
+
+impl ::core::default::Default for Bar {
+    #[inline]
+    fn default() -> Bar {
+        Bar(core::default::Default::default())
+    }
+}
+
+impl ::core::default::Default for Foo {
+    #[inline]
+    fn default() -> Foo {
+        Foo {
+            a: core::default::Default::default(),
+        }
+    }
+}
diff --git a/gcc/testsuite/rust/compile/nr2/exclude b/gcc/testsuite/rust/compile/nr2/exclude
index 512419438db..6f6280d3b66 100644
--- a/gcc/testsuite/rust/compile/nr2/exclude
+++ b/gcc/testsuite/rust/compile/nr2/exclude
@@ -123,4 +123,5 @@ derive-default1.rs
 issue-3402-1.rs
 for-loop1.rs
 for-loop2.rs
+issue-3403.rs
 # please don't delete the trailing newline